Polyamide-imide or polyamide-imide-phthalamides and polyaryletherketone blends yield mixtures that have two different glass transition temperatures, i.e., are immiscible. In the field of miscibility or compatibility of polymer blends, the prior art has found predictability to be unattainable, even though considerable work on the matter has been done. According to the authorities:
(A) "It is well known that compatible polymer blends are rare". Wang and Cooper, Journal of Polymer Science, Polymer Physics Edition, Vol. 21, p. 11 (1983). PA0 (B) "Miscibility in polymer-polymer blends is a subject of widespread theoretical as well as practical interest currently. In the past decade or so, the number of blend systems that are known to be miscible has increased considerably. Moreover, a number of systems have been found that exhibit upper and lower critical solution temperatures, i.e., complete miscibility only in limited temperature ranges. Modern thermodynamic theories have had limited success to date in predicting miscibility behavior in detail. These limitations have spawned a degree of pessimism regarding the likelihood that any practical theory can be developed that can accommodate the real complexities that nature has bestowed on the polymer-polymer interactions." Kambour, Bendler, Bopp, Macromolecules, 16, 753 (1983). PA0 (C) "The vast majority of polymer pairs form two-phase blends after mixing as can be surmised from the small entropy of mixing for very large molecules. These blends are generally characterized by opacity, distinct thermal transitions, and poor mechanical properties. However, special precautions in the preparation of two-phase blends can yield composites with superior mechanical properties. These materials play a major role in the polymer industry, in several instances commanding a larger market than either of the pure components." Olabisi, Robeson, and Shaw, Polymer-Polymer Miscibility, Academic Press, New York, N.Y., p. 7 (1979). PA0 (D) "It is well known that, regarding the mixing of the thermoplastic polymers, incompatibility is the rule and miscibility and even partial miscibility is the exception. Since most thermoplastic polymers are immiscible in other thermoplastic polymers, the discovery of a homogeneous mixture or partially miscible mixture of two or more thermoplastic polymers is, indeed, inherently unpredictable with any degree of certainty; for example, see P. J. Flory, Principles of Polymer Chemistry, Cornell University Press, 1953, Chapter 13, p. 555." Younes, U.S. Pat. No. 4,371,672. PA0 (E) "The study of polymer blends has assumed an ever increasing importance in recent years and the resulting research effort has led to the discovery of a number of miscible polymer combinations. Complete miscibility is an unusual property in binary polymer mixtures which normally tend to form phase-separated systems. Much of the work has been of a qualitative nature, however, and variables such as molecular weight and conditions of blend preparation have often been overlooked. The criteria for establishing miscibility are also varied and may not always all be applicable to particular systems." Saeki, Cowie and McEwen, Polymer, vol. 25, p. 60 (January 1983). PA0 "The most commonly used method for establishing miscibility in polymer-polymer blends or partial phase mixing in such blends is through determination of the glass transition (or transitions) in the blend versus those of the unblended constituents. A miscible polymer blend will exhibit a single glass transition between the Tg's of the components with a sharpness of the transition similar to that of the components In cases of border line miscibility broadening of the transitions will occur. With cases of limited miscibility, two separate transitions between those of the constituents may result, depicting a component 1-rich phase and a component 2-rich phase. In cases where strong specific interactions occur, the Tg may go through a maximum as a function of concentration. The basic limitation of the utility of glass transition determinations in ascertaining polymer-polymer miscibility exists with blends composed of components which have equal or similar (20.degree. C. difference) Tg's, whereby resolution by the techniques to be discussed of two Tg's is not possible." PA0 "Perhaps the most unambiguous criterion of polymer compatibility is the detection of a single glass transition whose temperature is intermediate between those corresponding to the two component polymers." PA0 4,4'-dihydroxybenzophenone, PA0 4,4'-dihydroxybiphenyl, and PA0 4,4'-dihydroxydiphenyl ether. PA0 4-(4-chlorobenzoyl)phenol, PA0 4,4'-difluorobenzophenone, PA0 4,4'-dichlorobenzophenone, PA0 4'-chloro-4'-fluorobenzophenone, ##STR14##
Thus, miscible or compatible polymer blends are not common. The criteria for determining whether or not two polymers are miscible are now well established. According to Olabisi et al., Polymer-Polymer Miscibility, supra p. 120,
W. J. MacKnight et al., in Polymer Blends, D. R. Paul and S. Newman, p. 188, Academic press, New York, NY. (1978) state:
In this passage, it is clear that by compatibility the authors mean miscibility, i.e., single phase behavior. See, for example, the discussion in Chapter 1 by D.R. Paul in the same work. The above references and related application are hereby incorporated by reference.
Based on applicants' knowledge, the prior art has failed to teach how to stabilize the melt viscosity of immiscible blends of this invention to avoid encountering an increase of the melt viscosity of the blend while it is being molded, for example, by injection molding. Applicants have discovered how to overcome a problem unsolved by the prior art for the subject blends and have discovered that products formed from them have improved physical properties compared to polyamide-imide products not alloyed with polyaryletherketones.